Enamines from the biomass derivative Cyrene and reactions with isocyanates and ketenes
To extend the chemical space accessible from the biomass-derived platform chemical Cyrene, enamines have been prepared and their reactions with selected electrophiles have been examined. The crystalline enamines prepared from morpholine (89% yield) and piperidine (79% yield) were stable and showed excellent reactivity with isocyanates, isothiocyanates and ketenes to give amides, thioamides or cyclobutanones, respectively.
Intermolecular Enamine Mizoroki–Heck Reactions on a Bio-Derived Scaffold
The intramolecular enamine-Mizoroki–Heck reaction allows for the construction of nitrogen-containing heterocycles, although the related intermolecular version is less known. The reactions of enamines derived from Cyrene were investigated under Mizoroki–Heck conditions. An optimization study was used to identify that 1.5 mol % Pd(dba)2 with PCy3 in xylene at reflux temperature gave the highest yield with electron-rich aryl iodides. Arylation occurred predominantly at the C–N center of the enamine, while the diastereoselectivity was dependent on the nitrogen substitution in the enamine.
Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions
A skeletal rearrangement of a series of 6,8-dioxabicyclo[3.2.1]octan-4-ols has been developed using SOCl2 in the presence of pyridine. An oxygen migration from C5 to C4 was observed when the C4 alcohols were treated with SOCl2/pyridine, giving a 2-chloro3,8-dioxabicyclo[3.2.1]octane ring-system via the chlorosulfite intermediate. Analogous allylic alcohols with endocyclic and exocyclic unsaturations underwent chlorination without rearrangement due to formation of allylic cations. The rearrangement was also demonstrated using Appel conditions, which gave similar results via the alkoxytriphenylphosphonium intermediate. Several reactions of the products were investigated to show the utility of the rearrangement.
Achieving High-Efficiency Organic Photovoltaics from a New Completely Amorphous Donor Polymer
The development of non-fullerene acceptors (NFAs) such as ITIC andY6 has greatly improved the efficiency of polymer solar cells. Therefore, focus should now shift towards the design of donor polymers with better compatibility with these NFAs to attempt to push efficiencies to higher levels. The indacenodithienothiophene (IDT) unit has up till now been typically incorporated into donor polymers for fullerene-based solar cells" however, the application of IDT-based polymers in NFA solar cells is rare. In order to increase the number of donor polymer candidates, we have synthesized two new polymers PIDT-T8BT and PIDT-T12BT conjugating IDT and perfluorinated benzothiadiazole moieties through octyl and dodecyl thiophene bridging units, respectively. These polymers were studied and revealed to be completely amorphous without aggregates, and their glass transition temperatures were distinct owing to the different lengths of the alkyl groups attached to the thiophene units. In addition, the length of the side groups greatly affects the solar cell performance. The longer dodecyl side groups in the polymer PIDT-T12BT resulted in a lower glass transition temperature and favorable thermal annealing conditions of the active layer blend with Y6. A promising power conversion efficiency of over 12% was achieved for PIDT-T12BT when paired with the Y6 acceptor and thermally annealed at 170 °C, which is the highest reported value so far for IDT-based donor polymers.